In general, loop coils and loop detection devices are frequently used so as to detect traffic information, such as whether or not a vehicle exists, and the travel velocity and type of a vehicle. Such a loop detection device detects the change of inductance produced in one or more loop coils by the movement of a vehicle or the like, thereby detecting the traffic information, such as whether or not a vehicle exists, the travel velocity and type of the vehicle. It has been reported that the change of inductance in such a loop coil is not affected by the road icing, the change of temperature and moisture, the change of sunlight hours, the characteristic change of a road surface, etc., and the loop coil detection devices as mentioned above have a reliability of no less than 99% under a practical environment.
The existing loop detection devices include one loop coil or two or more loop coils provided in a predetermined distance with the same purpose in a lane or place or a road, for which detection is desired, wherein the one loop coil or the two or more loop coils are installed in one or more lanes. The loop coils installed in each lane are connected to a loop detection device installed on the roadside, and the loop detection device transmits detected data to a traffic signal controller. At this time, the data processed in the loop detection device is transmitted to the traffic signal controller in a wired or wireless manner.
FIG. 1 shows a configuration of a conventional wired type traffic information detection system.
As shown in FIG. 1, the conventional wired type traffic information detection system transfers the change of inductance induced in a stop line sensing loop coil 2 and/or a straight ahead direction interruption sensing loop coil 3 by a vehicle to a loop detection device 4 installed in the roadside through a wire. The loop detection device 4 detects the electric change received from the loop coil 3, thereby detecting traffic information, such as whether or not a vehicle exists, the travel velocity and type of the vehicle, etc. The loop detection device 4 transmits detected data to a traffic signal controller 1 (an in-situ controller or a VDS controller) through a wire or the loop coil 2 is directly connected to a loop detection device existing within the traffic signal controller 1 through a wire so that the traffic information is processed on the basis of the signal outputted from the loop coil 2.
FIG. 2 shows a configuration of a conventional wireless type traffic information detection system.
As shown in FIG. 2, the conventional wireless type traffic information detection system wirelessly transmits electric change induced by a vehicle in a stop line sensing loop coil 12 and/or a straight ahead direction interruption sensing loop coil 13 provided in a lane or place, for which detection is desired, to a corresponding loop detection device 14 installed at a road side. The loop detection device 14 detects the electric change received from the loop coils 13, thereby detecting traffic information, such as whether or not a vehicle exists, and the travel velocity and type of the vehicle, etc. The loop detection device 14 wirelessly transmits the detected data to a traffic signal controller 11 (an in-situ controller or a VDS controller) with a transceiving antenna. The traffic signal controller 11 receives the data through the antenna and then converts the signal outputted by the loop coils by using an internal conversion device. Thereafter, the traffic controller 11 inputs the converted signal into a traffic information extraction device (not shown) within the traffic signal controller 11 so that the traffic information can be acquired.
However, with the above-mentioned conventional traffic information detection systems, the lifespan of a loop detection device is very short regardless of whether or not the loop detection device employs the wired communication type or the wireless communication type because the gas, electric or communication line construction frequently performed in the roadside or the pavement improvement or repair work causes a connection line cut-off between one or more loop coils installed on the lanes of the road and the loop detection device positioned at the roadside. This is the common problem of the conventional wired type and wireless type traffic information detection systems based on the existing installation method of connecting a lead-in wire of each loop coil to a loop detection device or a traffic signal controller installed at the roadside. Consequently, there is a problem in that a great public cost is wasted as the provisions installed at an enormous cost become useless due to a connection line cut-off occurring between a loop coil and a loop detection device as described above.